NR4A1 knockdown confers hepatoprotection against ischaemia-reperfusion injury by suppressing TGFβ1 via inhibition of CYR61/NF-κB in mouse hepatocytes

Nuclear receptor subfamily 4, group A, member 1 (NR4A1) can aggravate ischaemia-reperfusion (I/R) injury in the heart, kidney and brain. Thus, the present study aimed to unravel the role of NR4A1 on hepatic I/R injury. For this purpose, the mouse hepatic I/R model and H/R-exposed mouse hepatocytes model were established to stimulate the hepatic and hepatocellular damage. Then, the levels of ALT and AST as well as TNF-α and IL-1β expression were measured in the mouse serum and supernatant of hepatocyte s, respectively. Thereafter, we quantified the levels of NR4A1, CYR61, NF-kB p65 and TGFβ1 under pathological conditions, and their interactions were analysed using ChIP and dual-luciferase reporter gene assays. The in vivo and in vitro effects of NR4A1, CYR61, NF-kB p65 and TGFβ1 on I/R-induced hepatic and H/R-induced hepatocellular damage were evaluated using gain- and loss-of-function approaches. NR4A1 was up-regulated in the hepatic tissues of I/R-operated mice and in H/R-treated hepatocytes. Silencing NR4A1 relieved the I/R-induced hepatic injury, as supported by suppression of ALT and AST as well as TNF-α and IL-1β. Meanwhile, NR4A1 knockdown attenuated the H/R-induced hepatocellular damage by inhibiting the apoptosis of hepatocyte s. Moreover, we also found that NR4A1 up-regulated the expression of CYR61 which resulted in the activation of the NF-κB signalling pathway, thereby enhancing the transcription of TGFβ1, which was validated to be the mechanism underlying the contributory role of NR4A1 in hepatic I/R injury. Taken together, NR4A1 silencing reduced the expression of CYR61/NF-κB/TGFβ1, thereby relieving the hepatic I/R injury.